Field of the Invention
The invention described herein relates to medical fluid delivery applications and, particularly, to a system for the delivery of one or more medical fluids to a patient using a fluid path set with a turbulent mixing chamber, backflow compensator, and/or air bubble trap.
Description of Related Art
In many medical diagnostic and therapeutic procedures, a medical practitioner, such as a physician, injects a patient with a fluid. In recent years, a number of injector-actuated syringes and powered injectors for pressurized injection of fluids, such as contrast solution (often referred to simply as “contrast”), have been developed for use in procedures such as angiography, computed tomography (CT), ultrasound, and NMR/MRI. In general, these powered injectors are designed to deliver a preset amount of contrast at a preset flow rate.
Angiography is used in the detection and treatment of abnormalities or restrictions in blood vessels. In an angiographic procedure, a radiographic image of a vascular structure is obtained through the use of a radiographic contrast fluid which is injected through a catheter. The vascular structures in fluid connection with the vein or artery in which the contrast is injected are filled with contrast. X-rays passing through the region of interest are absorbed by the contrast, causing a radiographic outline or image of vascular structures containing the contrast. The resulting images can be displayed on, for example, a monitor and recorded.
In a typical angiographic procedure, the medical practitioner places a cardiac catheter into a vein or artery. The catheter is connected to either a manual or to an automatic contrast injection mechanism. A typical manual contrast injection mechanism includes a syringe in fluid connection with a catheter connection. The fluid path also includes, for example, a source of contrast, a source of flushing fluid, typically saline, and a pressure transducer to measure patient blood pressure. In a typical system, the source of contrast is connected to the fluid path via a valve, for example, a three-way stopcock. The source of saline and the pressure transducer may also be connected to the fluid path via additional valves, again such as stopcocks. The operator of the manual contrast injection mechanism controls the syringe and each of the valves to draw saline or contrast into the syringe and to inject the contrast or saline into the patient through the catheter connection.
Automatic contrast injection mechanisms typically include a syringe connected to one or more powered injectors having, for example, a powered linear actuator. Typically, an operator enters settings into an electronic control system of the powered injector for a fixed volume of contrast and saline, and a fixed rate of injection for each. Automatic contrast injection mechanisms provide improved control over manual apparatus where successful use of such manual devices is dependent on the skill of the medical practitioner operating the device. As in a manual system, the fluid path from the automatic contrast injection mechanism to the patient includes, for example, a source of contrast, a source of flushing fluid, typically saline, and a pressure transducer to measure patient blood pressure. The source of contrast is connected to the fluid path via a valve, for example, a three-way stopcock. The source of saline and the pressure transducer may also be connected to the fluid path via additional valves, again such as stopcocks.
When the contrast and the flushing fluid are injected, it is desirable for the two fluids to be mixed well before injection into the patient. However, because the contrast and the flushing fluid typically have different specific gravity and viscosity, the two solutions may not be thoroughly mixed using a known mixing valve, such as a T- or Y-shaped joint, or a three-way stopcock. As a result, when the contrast and the flushing fluid are not mixed properly, the resulting image taken by a fluoroscopic imaging apparatus may be uneven, thereby making it difficult to image the blood vessel clearly. Within the prior art, International Application Publication No. WO 2011/125303 discloses a mixing device for mixing two kinds of fluids. The mixing device includes a first inflow opening and a second inflow opening that is tangential to the first inflow opening to generate a swirling flow as the first and second fluids come into contact. The mixing chamber has a conical shape that is continuously narrowed to an outlet opening. However, existing solutions are often not adequate in promoting thorough mixing of the fluids when small amounts of contrast and flushing solution are introduced and/or when the injection duration is short. Additionally, such existing mixing devices do not compensate for backflow of the contrast or the flushing fluid.
An additional problem with the known multi-fluid injectors is that fluid backflow occurs in injections where a viscous first fluid is injected at a higher ratio than a less viscous second fluid. In such a scenario, before a uniform fluid flow is established, the fluid pressure of the more viscous first fluid that is injected at a higher ratio acts against the fluid pressure of the less viscous second fluid that is injected at a lower ratio to force the second fluid to reverse the desired direction of flow. After injection, pressures equalize, and the fluid injection system achieves a steady state operation where first and second injection fluids are injected at a desired ratio. However, in small volume injections, steady state operation cannot be achieved prior to the completion of the injection process and the total volume of first and second fluids being delivered. Thus, even though a desired ratio of first and second fluids may be 80% first injection fluid to 20% second injection fluid, the actual ratio due to backflow of the first fluid may be higher. This problem is further compounded with an increase in injection pressure. Utilizing check valves downstream of the syringes containing the first and second injection fluids only prevents contamination of the syringes from the backflow and does not address the accuracy of the final mixture ratio.
While manual and automated injectors are known in the medical field, improved fluid delivery systems having a fluid path that promotes turbulent mixing of two or more fluids introduced into a mixing chamber continue to be in demand in the medical field. Additionally, improved fluid transfer sets having a fluid path with a mixing device adapted for thorough fluid mixing are also desired in the medical field. Moreover, the medical field continues to demand improved medical devices and systems used to supply fluids to patients during medical procedures such as angiography, computed tomography, ultrasound, and NMR/MRI.